Flat panel displays typified by liquid crystal displays are used in a wide field, taking advantage of their characteristics such as thin, lightweight, and low power consumption characteristics. A liquid crystal display panel as a component of a liquid crystal display includes a liquid crystal cell and at least one polarizing film bonded thereto, in which a display is produced with polarized light by converting a change in the orientation of liquid crystal molecules to a change in viewing angle under an electric field. Therefore, the process of bonding the polarizing film to the liquid crystal cell requires high accuracy of position and angle. Thus, alignment is generally performed in the bonding process.
A conventional process of bonding an optical function film such as a polarizing film to a liquid crystal panel is performed using a piece of film, which is obtained by cutting, into a piece of a size corresponding to the cell size, an optical function film material in the form of a long continuous web. For the bonding of such a piece, a film manufacturer generally produces a piece of optical function film, inspects the piece, performs end face working of the piece, performs clean packaging of the piece, and transports the packaged piece to a panel manufacturer, who unpacks the piece and then bonds it to a liquid crystal cell. Unfortunately, such a bonding process needs inspecting, packaging, and unpacking each piece of optical function film, and therefore increases the manufacturing cost. Such a process also needs to repeat alignment of a liquid crystal panel and the bonding operation every time a piece of optical function film is bonded, which has a problem in that the tact time in the bonding process is long so that the productivity is low.
In view of such a problem, Patent Documents 1 and 2 propose that a series of steps should be performed, which include providing an optical film laminate that is in the form of a continuous web and includes an optical function film and a carrier film attached to one principal surface of the optical function film, cutting the optical function film at predetermined intervals along the longitudinal direction while leaving the carrier film of the laminate uncut, then peeling off the carrier film from the optical function film, and bonding the exposed surface of the optical function film to a liquid crystal panel.
FIG. 9 shows an example of the optical function film laminating device disclosed in Patent Document 2. The device of FIG. 9 includes a feeder 401 for feeding an optical film laminate, on which a continuous roll 350 including an optical film laminate 315 wound into a roll is mounted. The optical film laminate 315 is continuously fed from the continuous roll, and a cutting apparatus 403 cuts only the optical function film 310 into pieces of a predetermined length along the longitudinal direction while leaving the carrier film 313 uncut (hereinafter, such a method of cutting only the optical function film is called “half-cutting” as needed). A carrier film peeling apparatus 404 peels off the optical function film 310 from the carrier film 313, and in a laminating device 405, the exposed surface of the optical function film 310 peeled off from the carrier film 313 is bonded to a liquid crystal panel W supplied from a liquid crystal panel feeder 408 through another path.
When the optical function film feed path is provided with an inspection apparatus 402, any appropriate defect detection means 420 is used to detect any defects of the optical function film or markings attached to defective parts. Based on the information about the detected defect or marking position, the cutting apparatus can make the longitudinal length of cut pieces different between the defective part with any defect and the non-defective part with no defect, or the laminating device 405 can be controlled so that the defective part will not be bonded to the liquid crystal panel, which can increase the optical function film-use efficiency or the bonding efficiency.
In the apparatus of FIG. 9, accumulator rollers 407a and 407b are provided upstream and downstream of the cutting apparatus 403, respectively. Therefore, while an optical film laminate feeder 401 continuously feeds the optical function film and a carrier film take-up apparatus 406 continuously takes up the carrier film, the feeding of the film can be stopped in the cutting apparatus 403 when the film is cut by the cutting apparatus 403.
According to such a bonding method, feeding the film from the continuous roll 350 including the optical film laminate 315 wound into a roll, cutting the optical function film, and bonding the optical function film to a liquid crystal panel can be automatically and continuously performed in a series of steps, so that the bonding process time can be significantly reduced. On the other hand, such a method has a problem in that the control of the system is complicated, because the cutting step in which half-cutting is carried out by the cutting apparatus 403 and the bonding step in which the optical function film 310 and the liquid crystal panel W are bonded together by the laminating device 405 are in series. In addition, the cutting step involves stopping the feeding of the film, cutting the film, and resuming the feeding, and therefore is a bottleneck in reducing the tact time.
On the other hand, Patent Document 3 discloses a continuous roll of an optical film laminate in the form of a continuous web, which has previously undergone a defect inspection and includes an optical function film with score lines each formed along the widthwise direction. If the continuous roll with score lines formed by half-cutting in advance is mounted on a supporting unit 212 of an optical film laminate feeder 201 shown in FIG. 7 and used in successive bonding of the optical function film and the liquid crystal panel, there is no need to perform, in series, the bonding step and the cutting step, which is the rate-determining step in such a bonding method as disclosed in Patent Document 2. Therefore, the use of such a scored continuous roll as disclosed in Patent Document 3 can further reduce the process time, as compared to such a bonding method as disclosed in Patent Document 2.